用r计算气象站数据的平均值

Question

我正在使用一个大约800个气象站的数据集，每个气象站从1986年到2014年的月气温值。数据分为三列：(1)桩号名称、(2)日期(年和月)和(3) Temp。一般而言，数据如下所示：

STATION    DATE    TEMP
Station 1  198601  -15
Station 1  198602  -16
Station 1  201401  -10
Station 1  201402  -14
Station 2  198601  -11
Station 2  198602  -9
Station 2  201401  -5
Station 2  201402  -4

我需要提取不同年份范围内给定月份的每个气象站的平均温度。例如，如果我需要知道1986-1990年间每个气象站7月份的平均气温。我的理想输出是一个新的列表或数据帧，它根据我指定的日期范围给出每个站点的平均温度。

我确信这可以使用for循环来完成，但我不太擅长创建这样的代码。任何建议都将不胜感激。

Answer 1

使用dplyr代替数据表

weather <- data.frame(station = c("Station 1", "Station 1", "Station 1", "Station 1",
                              "Station 2", "Station 2", "Station 2", "Station 2"),
                  date = c(198601, 198602, 201401, 201402, 198601, 198602, 201401, 201402),
                  temp = c(-15, -16, -10, -14, -11, -9, -5, -4))


library(dplyr)
library(stringr)
# get month and year columns in data
weather <- mutate(weather,
              year = str_extract(date, "\\d{4}"),
              month = str_extract(date, "\\d{2}$"))

# get the mean for each station for each month
mean_station <- group_by(weather, station, month) %>%
  summarise(mean_temp = mean(temp, na.rm = T))

如果只需要在特定的日期范围内执行此操作，则可以按年份添加筛选器

mean_station <- group_by(weather, station, month) %>%
  filter(year >= 1986, year <= 2015) %>%
  summarise(mean_temp = mean(temp, na.rm = T))

Answer 2

像这样的东西...？

> df$month <- substr(df$DATE, 5, 6)
> result <- aggregate(TEMP~STATION+month, mean, data=df)
> data.frame(Year=unique(substr(df$DATE, 1, 4)), result)
  Year  STATION month  TEMP
1 1986 Station1    01 -12.5
2 2014 Station2    01  -8.0
3 1986 Station1    02 -15.0
4 2014 Station2    02  -6.5

Answer 3

或者也许

library(data.table)
setDT(df)[, list(MeanTemp = mean(TEMP)), 
                by = list(STATION, Mon = substr(DATE, 5, 6))]

#      STATION Mon MeanTemp
# 1: Station 1  01    -12.5
# 2: Station 1  02    -15.0
# 3: Station 2  01     -8.0
# 4: Station 2  02     -6.5